I would not call the prop brittle but it is not super strength either. This is by design. When a prop strikes the ground or an object, you actually want it to break. If the prop does not break, worse things happen. For example, motor shafts can bend, motors can be damaged, or firewalls and motor mounts can be loosened or ripped out of the plane entirely. You can use a more flexible prop but the performance suffers. You want a nice stiff prop for performance purposes but you also want it to give or even blow apart when it hits something so nothing which is more expensive and more difficult to repair is broken. I would consider the prop to be the sacrificial lamb.